The present invention relates to a heat exchange injector suitable for use in an expander cycle rocket engine. More particularly, the present invention relates to a heat exchange injector including a double helix member for encouraging gasification of an oxidizer in a rocket engine operating over a broad throttle range, e.g., from about full thrust to about 5% of full thrust.
In a liquid propellant rocket engine, a fuel (e.g., liquid hydrogen) and an oxidizer (e.g., liquid oxygen) are pumped into a combustion chamber, where they burn to create a high pressure and high velocity stream of hot gases. A nozzle subsequently accelerates the hot gases further. The hot gases exit the nozzle, thereby creating thrust.
One type of bipropellant rocket engine, which uses a separate fuel and oxidizer, is an expander cycle which, because of its relative simplicity, is preferred in orbit transfer or descent/ascent rocket engine missions where maximum flexibility and ease of operation is required. In one type of an expander cycle, fuel is heated by heat from a main combustion chamber of the rocket engine. More specifically, liquid fuel is fed into coolant passages in the walls of the combustion chamber. The combustion chamber heats the fuel, while the fuel simultaneously cools the combustion chamber. When the fuel is heated to a certain temperature, the fuel undergoes a change from liquid to gaseous state. The pressure from the expansion of the fuel creates pressure, which drives the turbines that drive fuel and oxidizer pumps.
A bipropellant expander cycle rocket engine also includes an injector, where fuel and oxidizer are metered, mixed, and ignited into the combustion chamber in a controlled manner. A heat exchange injector utilizes heat from gasified fuel (which is gasified by the heat of the combustion chamber during the expansion cycle) to gasify the oxidizer.